Instrument for recording or measuring the size and shape of surface irregularities



Dec. 9, 1952 Filed Oct. 8, 1949 GENE/0170!? D. PRI EST INSTRUMENT FOR RE ORDING OR MEASURING THE ES 3 Sheets-Sheet 1 SIZE AND SHAPE OF SURFACE IRREGULARITI OUTPU T k INVENTOR DORMAA/ E. PR/[ST A ORNEY Dec. 9, 1952 D. E. PRIEST 2,620,655 INSTRUMENT FOR RECORDING OR MEASURING THE SIZE AND SHAPE OF SURFACE IRREGULARITIES Filed Oct. 8, 1949 3 Sheets-Sheet 2 7 J Y I 73 I I 0) 1 INVENTOR D RA/AME. PR/[ST A RNEY Dec. 9, 1952 2,620,655

DQE. PRIEST INSTRUMENT FOR RECORDING OR MEASURING THE SIZE AND SHAPE OF SURFACE IRREGULARI-TIES Filed Oct. 8, 1949 s Sheets-Sheet s ammn me 39 mvzm-oa F/G. 4 Ara/WAN; PHIL-$7 ORNEY Patented Dec. 9, 1952 INSTRUMENT FOR RECORDING OR MEAS- URING THE SIZE AND SHAPE OF SURFACE IRREGULARITIES Dorman E. Priest, North Lexington, Mass, as-

signor to Physicists Research Company, Ann

Arbor, Mich.

"Application October 8, 19419, Serial No. 120,328

20 Claims. I

The present invention relates broadly to improvements in instruments for indicating or recording the sizes and shapes of surface irregularities, for example, irregularities of the surfaces obtained by various machining and finishing operations, and in its specific phases it relates to an instrument adapted for use in recording the profile of surfaces of that general character.

Considerable development work has been carried' on in connection with electrical methods of measuring such quantities, and the greatest progress along this line has been made in measuring such quantities quite rapidly so that the electrical frequencies involved normally range from 10 cycles per second to several thousand cycles per second and upward. An important development in that field is covered by U. S. Patent No. 2,240,278 granted to Ernest J. Abbott. A fundamental limitation of the apparatus of that invention'is that it will not measure static displacements or slow movements which are below the low frequency cut-off point of the assembly. Generally speaking, the present invention, which is a continuation-in-part of my co-pending patent application Ser. No. 555,942, filed September 27, 1944, now abandoned in favor of this application and application Ser. No. 120,329, filed October 8, 1949, is an improvement on the referred to invention of Ernest J. Abbott in that it makes possible both static and dynamic measurements of small dimensional changes or displacements, and so far as either static or dynamic measurements are concerned, it is not efiected by low frequency cut-off conditions.

Others have devised specific methods of effecting electrical measurements of static displacements of one type or another, but each of those methods has specific limitations which interfere field of profile recording. For instance, variable condenser types of converters are necessarily high impedance devices and therefore subject to stray capacitance eifects and pick-up. The use of two symmetrical coils, and a movable iron element whose movement will vary the inductthrough thebalanc point; "A'fine wire hasbeen substituted'for balanced coilunits in converters,

whelieinvaried resistance of the wire is obtained by stressing it. This'wire is'also affected by temwith, and reduce its usefulness, especially in the 7 2 perature changes and the circuit itself i subject to the inherent bridge circuit balancing difficulties. Piezo-electric crystals have also been used in devices for making measurements of displacements. However, under static load the electric charge leaks off the surface of the stressed crystal in a short time and makes the readings based on same inaccuratej In addition, crystals are high impedance devices and in actual practice much difiiculty is experienced with pick-up and stray capacitance effects. Another form of converter mechanism is one which utilizes a movable iron armature which affects a suitable pick-up coil or coils. This armature is mounted in the path of an alternating magnetic flux so that the amount of flux linking the pick-up coil or coils varies with the position of the armature relative to the field structure. In addition to electrical limitations of this type of apparatus, the moving iron element, in order for the apparatus to develop a useable sensitivity, must have substantial mass, and that in turn, means that its mechanical impedance is necessarily great. This not only limits its ability to follow high frequencies, but also require sizeable operating forces even at low frequencies. In profile recording it is necessary to use tracer points of substantially less than 0.001 diameter, so that exceedingly minute operating forces must be used in order to avoid damage to the point, specimen, or both. It was a recognition of the shortcomings of this type of apparatus, as well as those of the other prior art constructions described above, and a knowledge of the need of a suitable apparatus for measuring or recording surface profiles, which led to the conception and development of the present invention. In particular, the present invention makes possible the recording of nonrecurrent surface irregularities such as plateaus, steps, bows, and slopes, as well as long wave length irregularities classified as waviness, 'and also closely-spaced irregularities classified as roughness. Irregularities with spacings less than 3% are classified as roughness, while those with spacings greater than 3 2" are classified as waviness. 7

Accordingly, among theobjects of the present invention is the production of a highly flexible and sensitive apparatus for measuring or recording the sizes and shapes of surface irregularities over a very wide range of spacings as well as heights. i I M l "Another object is to provide an apparatusfor measuring or indicating dimensional characteristicsof asurface wherein bridge circuits or'mov- 3 ing iron armatures with their shortcomings are avoided.

Another object is toprovide an apparatus where the moving parts are of light weight so as to have a low mechanical impedance.

Another object is to provideanelectrical device including a converter, the output of which is instrinsically linear throughout its operating range, such range being pre-chosen and the elements of the assembly designed to handle that range.

Another object is to provide an apparatus adapted for use in indicating or recording surface profiles.

Still further objects and advantages will rippear as the description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the mechanical-electrical means hereinafter fully described and particularly pointed out in the claims, the annexed drawings, and the following description setting forth in detail certain means for carrying out the invention, such disclosedmeans illustrating, however, but several of various ways in which the principle of the invention maybe used.

In the annexed drawings:

,Figure 1 shows an assembly of a preferred form of profile recording apparatus particularly adapted for making linear investigations, and wherein certain of the electric circuit elements are diagrammatically illustrated.

Figure 2 shows an assembly adapted for use in investigating the profile of circular or cylindrical objects with the electrical output of such apparatus deliverable to an electric circuit such as is shown in Figure 1.

Figure 3 shows a modified form of the displacement converter of the Figure 1 assembly, and wherein the positioning coil is connected in series with a third coil suitably mounted in the magnetic flux field of the converter. 7

Figure 4 shows another modified form of the displacement converter of Figure 1, and wherein a third coil in the converter is used to produce a bucking voltage utilizable in the input and phasing network.

Referring more particularly to Figure 1 of the drawings, the stationary body member I, with its vertical ways 2 and 3, has mounted thereon for vertical movement, a support member 4 carrying a horizontal piloting slide 5, which in turn carries converter assembly 6. The horizontal piloting slide 5, has mounted on its underface, a suitable threaded nut 1, in engagement with screw 8 which is suitably supported at its ends and carries pulley 9, which is driven by a reversible motor l0, through belt H.

The vertical position of the support 4 (Figure 1), is adjusted by means of crank l2, which operates threaded shaft I3, and that shaft in turn engages a suitable threaded portion (not shown) of support 4. A conventional locking means (not shown) is used for holding the assembly in an adjusted position. Length-of-trace adjustment blocks i4 and 15, mounted on piloting slide 5, and which may be conveniently locked in place by means of suitable thumb screws l6 and H, are used to actuate a suitable motor operation-limiting switch 18, which is carried on support 4. A conventional switch I9, is used for controlling the operation of motor In.

Stationary body member I (Figure 1), is rigidly fastened to a base plate 20, and an alinemfint table 2|, preferably having two fixed legs 4 22, and one adjustable leg 23, rests on this base plate and carries on its upper face a specimen 24, the surface of which is to be linearly investigated by contact with a suitable tracer point 25 which projects from converter assembly 6. In actual use, the support 4 is suitably adjusted up or down, following which alinement itable 2| is adjusted by means of adjustable leg 23 so that the surface of the specimen is suitably alined in the direction of movement of piloting slide 5 carrying the converter assembly 6. With the specimen in adjusted position, tracing motion is performed when switch I9 is thrown to operating position and the converter assembly is :moved substantially parallel to the specimen surface while the :tracer point is in contact with such surface and limited to motion substantially perpendicular thereto.

Case 2.6 of the converter assembly 6 contains an outer pole member 27 and an inner pole member 28 concentric therewith. These two pole members, which are made of suitable material for carrying alternating magnetic flux, are fastened together in conventional manner, for instance, by means of screws 29 (Figure 3). The gap 30 between the free endsof the outer and inner poles is substantially uniform and moderately'long. Mounted for movement axially in gap 30 is a relatively short positionin coil 3| mounted on .a light-weight coil form 32. This coil form is mounted on the end of stem 33 which is supported by a pair of cantilever leaf springs 3' 1 and 35 which are joinedto case 26 by means of a conventional spacing block 36. Stem 33 projects through a suitable opening 31 in end plate 38 and carries contact tracer point 25. The particular form of the tracer point will depend upon the type-of investigations to be made. For surfaceroughnessmeasurements a hemispherical tracer tip of from .00005" to .0005" tip radius is very satisfactory, and a conventional material from which to make same is diamend. To determine waviness of a surface the tracer tip may have a larger radius.

An exciting coil 39 is used to produce the alternating magnetic flux in pole pieces 27 and 28. This flux crosses gap 30, and by linking positioning coil 3! therein, produces an alternating carrier voltage in that coil. 'The amplitude of said carrier voltage depends upon the relative position of the positioning coil 3| in gap 30. Thus, the voltage produced in the positioning coil 3| is amplitude-modulated in step with 'the'mechanical axial displacements of said coil.

Referring again to Figure .1, it will be noted that an input and phasing network it! has been indicated as included within the dashed lines. A preferred form of the input and phasing network circuit will now be described. The output of positioning coil 3! is passed to input and phasing network 36 which also serves as a range selector providing a .set of predetermined sensitivities. From the input of network it, the voltage passes through a step-up input transformer 4i and a phasing network 88 to a stepped signal-attenuator s2. A pre-chosen, constant alternating current voltage is supplied by generator 43 to a stepped neutralizing-attenuator 44 which is ganged by mechanical coupling 45 to stepped signal-attenuator 42 so that the two may be operated in synchronism. An isolating transformer 4-6 is also connected to generator 43 and delivers a voltage to control-resistor 41. The voltage appearing on the input terminals of the amplifier network 45.

48 is obtained through the circuit .connections between the amplifier, control resistor 41, and the two stepped attenuators 42 and 44, and is the algebraic addition of the alternating current voltages selected by each of the above mentioned controls, said voltages appearing between the movable contact arms on the controls and their respective ends J, K, and L. Phase adjusting network 88 is adjusted so that the voltage across stepped signal-attenuator 42 is substantially 180 out of phase with the voltage across stepped neutralizing-attenuator 44. Stepped signal-attenuator 42 attenuates the output of the positioning coil 3| in discrete, chosen steps, thus permitting selection of different sensitivities. In order that the magnitude of the voltage appearing on the input of amplifier 48 may remain substantially constant for these different sensitivities, the neutralizing voltage which is subtracted from that obtained from the positioning coil 3|, and which is obtained from. neutralizing-attenuator 44, is also attenuated in chosen, discrete steps. This results in selected positions of the mechanically ganged control offering a choice of over-all electrical magnifications between the displacement of positionin coil 3| and the displacement of the pointer on a suitable indicator 49. After the voltage algebraically added to that appearing across signal-attenuator 42 has been approximately adjusted in relatively large steps by neutralizing-attenuator 45, it may be more finely adjusted by control resistor 4?. Since the magnitude of the voltage algebraically added to that appearing across signal-attenuator 42 affects the reading of indicator 49 for a given rest position of positioning coil 3|, control resistor 4'! may be used to adjust said reading to a predetermined zero without affecting sensitivity.

The output from the input and phasing network 49, is amplified in amplifier 5S, and de livered to a band-pass filter unit 58. Band-pass filter unit 5|! reduces the amount of extraneous voltages which appear in amplifier t8, and allows the narrow band of frequencies used in the measurement to be transmitted substantially without interference. The filter output is delivered to a rectifier circuit 5|. This rectification provides demodulation of the amplitudemodulated carrier so that voltages of frequencies corresponding to the displacements of tracer point 25 are obtained. The output of rectifier 5| is delivered to output network 52.

Generator 43 also delivers a pre chosen and constant alternating current voltage to rectifier circuit 53, and the pre-chosen"constant direct current output of the latter is delivered to output network52, but is'of opposite polarity to the input thereto from rectifier circuit 5|, so as to substantially cancel out the remainingminimum voltage not neutralized in input "and phasing Under these conditions, the instantaneous value of any voltage appearing in the output of the network 52 is, for all practical purposes, due entirely to a displacement of the positioning coil 3| from the pre-chcsenero or reference position of same. These instantaneous voltages are thus obtained by the .demodulating action of rectifier 5| on the amplitude-modulated carrier voltage appearing in amplifier 48. These instantaneous voltages are then further amplified by adirect current amplifier 54 whose output is applied to the indicating or recording t r A, sui b e. y e f ec rde i on s o a1 2A Qnv 1. :ty e o mo em nt j'qar nsa pointer which may be arranged to indicate, or

6 tomark directly on amoving chart. The amplifier 54 and DArsonval type recorder, 49. are well recognized to have characteristics suitable for followingthe variationsv of voltage correspondingto the mechanicalaxial displacements of coil 3|, but not the carrier frequency. Such chart ispreferably motor driven at a 'predeter mined and chosen rate of speed. The ratio of this speed to the tracing motion speed of the converter assembly determines the magnification along the chart, and the calibration of the above described electrical circuits determines the magnification across the chart. Thus a suitably ene larged profile curve of the specimenis recorded. Themagnification of the profile curve obtainable through the ccmbinaticn set forthlabove, makes possible the recording of inequalities of a surface profilein amounts substantially as small as one microinch. g

Another type'of apparatus utilizing the'present invention is illustrated in Figure 2 wherein supporting frame, 55 carries a motor 56 conventionally coupled to an adjustable speed1reducerg51 which, in turn, has an output pulley 58. Belt 59 connects pulley 58 to pulley 6|! which .is mounted on the vertical pilotingshaft 6|, which, in turn,'passes through piloting bearing 62. .On the lower end of vertical piloting shaft 6| is mounted a headme'mber 63 which carries a radial 'movement member 64, the movement'of which is controlled by crank .65 and screw 66. Supported by the radial movement member 64 is aconverter assembly 6a. 1

Mounted on the base portion 61 (Figurez) of supporting frame 55 is a compound member 68 of conventional design which includes a crank 69 connected to a conventional. threaded shaft'l'il for moving cross slide 1| crosswise of the assembly. Crank 12-is mounted on shaft 13 which, initurn, is mounted-in cross slide, H and is threadedly connected to cross slide 14 and prolvidesmove'ment .in a direction normally at right race 19 of a ball bearing, is mounted on the upper face of leveling table !5 and adjusted by means of operating cranks (it-and E2 until its vertical center line coincides with the vertical center line of vertical piloting shaft 5!. With the specimen 19 thus leveled and alined, the converter assembly 6a is adjusted by means of crank 65 until contacting tracer point 25 lightly rests against the surface of the specimen to be investigated. To provide clearance, a beam type converter is preferably .usedhere. This converter. is substantially the same as the converter shown in Figure 1 except that tracerpoint 25 is mounted on the end of a resiliently mounted beam which is carried on a suitable pivot 8|,

pulley 58, and belt 59 connecting pulleys 58 and 60, to rotate vertical piloting shaft'fil and carry converter assembly 6a aroundspecimen 19' very 7. slowly. A partor full revolution of the .piloting shaft-is normally all that isrequired for an investigation, although same may be repeated as often as. desired. For example, to investigate the surface of a 1 inner race of a ball bearing for waviness, a speed of approximately 2 R. P. M., is satisfactory. On the other hand, to check the same ball race for roughness, a speedof approximately .R,. P. M., is satisfactory. These speeds are merely given by way of exampleand same are not to be considered as a limitation of the invention. When converter assembly 6a is moved around inner race '19, the tracer point 25 will move radially as the surface of inner race 19 varies from a true circleconcentric with the center line of vertical piloting shaft 6 I. This movement of the contacting tracer point in turn actuates the positioning coil on the other end of beam 89 to thus modulate the carrier? voltage which is. delivered. to, an, electricalcircuitaspreviouslydescribedp 1.11

A modified form of theconverter assembly .6, shown in the Figure 1. combination, isdiagram matically illustrated asfib inliigure 3. This con,- verter assembly involves theuse of a. third coil 83 on. the alternating magnetic flux circuit of the assembly. This thirdcoil 83 is connected in series with positioning coil 31 to algebraically adjust, in desired directionandamount, the out: put voltage of the combinatiom This adjust:- ment in no way affectsthe modulation obtained by varying the position of positioning co l, 31 lengthwise of gap 30. The, combined 'outpl ?v of positioning coil 3| and, third coil, 83. is carried by leads 84 and 85 to the inputandphasingnet work 40 for handling as previously described. With the third coil 83 connected in series with the positioning coil 3], the. output or carrier voltage of the. converter for a given position of the positioning coil can be adjusted by adjusting the voltage supplied by the. third coil. However, the rate of change of theamplitude of the carrier voltage with the displacement of. the positioning coil will beunaffectedby the amount of voltage supplied by thethird coii. This is due to the fact that the modulation of the carrier. voltage is determined onlyby the change in flux linkages of the positioning coil. This facilitates the production of interchangeable converter as.- sembles, since the amplitude of the converter output voltage and the derivative of said output voltage with respect to the position of coil 3 can be set independently. V V V Figure 4 diagrammatically shows. another modification of the converter assembly wherein a third coil 83a forms part of an alternating current bucking circuit adapted for use in the circuit of Figure 1. In this cornbinationtheprechosen, constant alternating current voltage, delivered to input and phasing network lgbyrneans of leads 85? and 81 is obtainedv from the third coil 83 which links a suitable portion of the magnetic flux circuit such as pole 28 of the conveter assembly 60. Since this voltage is more nearly of the same wave shape as that received from positioning coil 3|, neutralization of the minimum voltage delivered by the positioning coil to the input and phasing network 40 is more readily accomplished.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the com binations herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I, her forepa c lar vpoieio t anddisunctly claim asmy invention": h

1. A surface profile measuring instrument-ca;- pable of indicating or, recording irregularities of the surface of aj specimen to be investigated, which comprises a converter assembly including a tracer point, a positioning coil, means for connecting said positioning coil to said tracer po nt for movement instep with the mechanical disf em s t e m n er ount ng said connecting means in saidconverter assembly so as. to restrict said tracer point to movement sub: stantially perpendicular to said specimen sur face, fixed electromagnetic means for convert? i s said m n al.disnl entsoi s id. ositiflninecoil nto m l tude. modul o s o acqustant frequency alternating voltage as said tracer point is moved along v and in contact With the surface of said specimen, means for supporting said converter assembly, means for movin gl said support so that said converter assemblyinoves substantially parallel to the surface of said speci men under investigation, means for supporting said movable support means, a demodulating electric circuit means for receiving said modulat ed voltage and demodulating. same, and-means for indicating said demodulated voltage so as to show the irregularities of the surface of said specimen being investigated.

2. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magnet flux, a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular tosaid specimen surface, said fixed magnetic circuit means having a gap, and said positioning coil being movable in said gap, an exciting coil for use in producing alternating magnetic flux in said fixed magnetic circuit means, means for supplying alternating-current electric power to said exciting coil thus inducing in said positioning coil a voltage whose frequency is that of 'said alternating-current power and whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, means for supporting said converter assembly, means for moving said support so that said converter assembly moves substantially parallel to the surface of said specimen under investigation, means for supporting said movable support means, a demodulating electric circuit means for receiving said modulated voltage and demodulating same, and means for indicating said demodulated voltage so as to show the irregularities of the surface of said specimen being investigated.

3. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, .means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement sub stantiallyperpendicular to said specimen surface, fixed electromagnetic means for converting said mechanical displacements of said positioning-coil into amplitude modulations of a constant-frequency alternating voltage as said tracer point is moved along and in contact with the surface of said specimen, means for supporting said converter assembly, means for moving said support so that said converter assembly moves substantially parallel to the surface of said specimen under investigation, means for supporting,

said movable support means, a demodulating circuit including a sensitivity adjusting circuit, an amplifier, a rectifier arranged to demodulate said amplitude-modulated carrier voltage, and means for indicating said demodulated voltage so as to show the irregularities of the surface of said specimen being investigated.

ing said mechanical displacements of .said posi--v tioning coilinto amplitude modulations of a constant-frequency alternating voltage as said tracer point ismovedalong andlincontact with: the sure.

face of said specimen, means for supporting said converter assembly, means for moving said support so that saidconv'erter assembly moves substantially parallel to the .surfaceof said speci men under investigation, means for supporting said movable support means, a demodulating electric circuit means for receiving said modulated voltage and demodulating same,,indica ting means responsive to said demodulated voltage, said indicating means comprising a graphic re:- cording means adapted to record on a suitable medium a graph whose coordinates are substantially proportional tothe corresponding dimensions of said irregularities actuating said tracer point. r

5. A surface profile measuring instrument capable of indicating or recording non-recurrent irregularities such as plateaus, steps-bows, and slopes as well as oscillatory irregularities of the surface of a specimen to be investigated-which comprises means for supporting said specimen in' position for profileinvestigatiom; a converter assembly including a fixed magnetic circuit means for carrying alternating magnetic'flux, a tracer point, a positioning coil, means for connecting'said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, resilient means for mounting said connecting means in said converter assembly so as to restrict said tracer point 'to movement substantially perpendicular to said spciriiensurface, saidfixed magnetic circuit means having an annular pole gap, and said positioning coil being axially movable in said gap and approximately centered longitudinally thereof, an exciting coil for producing alternating magnetic flux in said magnetic circuit means, means for supplying a constant alternating voltage'to said exciting coil thus inducing in said positioning coil a voltage whose frequency is that of said alternating voltage and whose amplitude is modulated in accordance with the varying position of said positioning coil in said gap of said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, means for supporting said converter assembly, means for moving said support so that said converter assembly moves in a path substantially parallel to the surface of said specimen under investiga tion, means for supporting said movable support means, an electric circuit means for receiving said modulated voltage and demodulating same, an amplifier for amplifying said demodulated voltage, and an indicating means responsive to said demodulated and amplified voltage, said indicating means comprising a graphic recording means adapted to record on a suitable medium a graph Whose coordinates are substantially proportional to the corresponding dimensions of said irregularities actuating said tracer point.

6. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magnetic flux, a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement instep with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular to said specimen" surface, said fixed magnetic circuit means having a gap, andsaid positioning coil being movable in said gap, an exciting coil for use in producing alternating magnetic flux in said fixed magnetic circuit means, means for supplying alternating-current electric power to said exciting coil thus inducing in said positioning coil a voltage whose frequency is that of said alternating-current power and Whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact With the surface of said specimen, a third coil mountedon said magnetic circuit andinductively linked with said alternating magnetic flux thereby inducing in said third coil an alternating voltage of frequency the same as that of said alternating-current electric power, and of magnitude determined by said magnetic linkage, means for connecting said third coil in series with said positioning coil so that the voltage output of said converter assembly is the algebraic sum of the voltages induced in said two coils, said output'voltage being amplitude-modulated to the extent that said positioning coil voltage is modulated, means for supporting said movable support means, a demodulating electric circuit means for demodulating said modulated output voltage, and means for indicating said demodulated voltage so as to show the irregularities of the surface of said specimen being investigated.

7. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assemblyincluding a fixed magnetic circuit means for carrying alternating magnetic flux, a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement instep with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular, to said specimen surface, said fixed magnetic circuit means having a gap, and said positioning coil adage-' 11 V being movable in said gap, an exciting coil for use'in producingalternating magnetic'fiux'in said fixed magnetic'circuit means, means for supplying alternating-current electric power to said exciting coil thus inducing in said positioning coil a voltage Whose frequency is that of said alternating-current power and whose amplitude is modul'atedin accordance with the varying position of said coil with respect to said fixed ma netic circuit means as said tracer point is'moved along "and in contact with the surface of said specimen, means for supporting said converter assembly, means for moving said support so that saidconv'erter assembly moves substantially parallel'to'the surfaceof said specimen'under investigation, means for'supporting said movable support means, a sensitivity adiusting circuit including a stepped attenuator receiving the amplitudemodulated output voltage of said converter assembly,'a second 'steppedattenu'ator receiving a substantially fixed'alternating voltage from'said means for supplying alternating-cur'rent power, electric circuit mean's'for'adjusting thevoltag'es across said two attenuators to substantially 180 phase opposition, mechanical ganging' means for simultaneous operation of'said two attenuators, leads for connecting the outputs of said two attenuators in series, thereby obtaining anamplitude-modulated output voltage from said sensitivity adjusting circuit, a demodulating'electric circuit means for receiving'said modulated'voltage and demo'dulating's'amaand means for'indica'tingsaid demodulated voltage so as to show the irregularities'of the surfaced-s id specimen beinginves'tigated. 7 w

8. A surface profileme'asuring instrument cap'able' 'of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magnetic flux, a tracer 'point,a"positioning c'oil, means for connecting said positioning coil to said tracer point for movement in stepwith the mechanical displacementsthereoh' means for mounting said connecting means in said converter assembly so as to restrict'said'tracer point to movement substantiallyperpendicular to said specimen surface, said fixed magnetic circuit means having a gap, and said positioning coil beingm'ovable in said gap, an exciting coil for use in producing alternating magnetic flux in said -fixed magnetic circuit means, means for supplying alternating current electric power to said exciting coil thus inducing in saidiposition ing coil a voltage whose frequency is that of said alternating-current power and whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, a third coil mounted on said magnetic circuit means, and inductively linked with said alternating magnetic flux thereby inducing in said third coil an alternating'voltage of frequency the same as that of said alternating current electric power and ofmagnitude determined by said magnetic linkage, means for supporting said 7 converter assembly, means for moving said support so that said converter assembly moves substantially parallel to the surface of said-specimen under investigation, means for supporting said movable supportm'eans, a sensitivity adjusting circuit including a stepped attenuator receiving the amplitude-modulatedoutput voltage of said converter assembly, a second's'tepped attenuator I2 7 l receiving a substantially fixed alternating "voltage from said third coil in said converter assembly, electric circuit means for adjusting the voltages'acro'ss said two attenuatorsto substantially phase opposition, mechanical gan'ging means for simultaneous operation of said two attenuators, leads for connecting the outputs of said two attenuators in series, thereby obtaining" an amplitude modulated output voltage from said sensitivity adjusting circuit, a'demodnlating ele tric circuit means for receiving saidmodulate'd voltage and demodulating same, "and meansfor indicating said demodulated voltage so'as to'sho'w the irregularities of the surface of said specimen being investigated.

9. A surface profile measuring instrument capable of indicating or recording irregularities of Y the surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magnetic flux, atracerpoint ,:apositioning coil, means for connecting said positioning coil to said tracer point for movement step with-the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular :to said specimen surface, said fixed magnetic circuit means having a gap, and said positioning coil being movable in said gap, anexciting coil for producing alternating magnetic fluxin said fixed magnetic circuit means, means for supplying alternating-current electric power to :said ex-. citing coil thus inducing insaid positioning coil a voltage whose frequency is that of said'altere nating-current power and whose amplitude is modulated in accordance with the 'varyingjposi'e tion of said coil with respect to said fixed magnetic circuit means as saidtracer pointis moved along and in contact with the surface of said specimen, means for supporting said converter assembly, means for moving said support so that said converter assembly moves substantially parallel to the surface of said specimen under investigation, means for supporting said movable support means, a demodulating circuit including a sensitivity adjusting circuit, an-amplifier, and a rectifier arranged to demodulate said ampli-e tude-modulated carrier Voltage, means for supplying a constant alterhating'Voltage, a second rectifier receiving saidalternating voltage and delivering a constant direct'curr'ent'volt'agesubstantially equal to the direct current voltage output of said first rectifier, an output network arranged to receive the outputs of said-tworectifiers and subtract said direct voltages so as'to leave substantially only *said demodulated voltage, and means for indicating said demodulated voltage so as to show the irregularities of *the surface of said specimen being investigated.

10. A surface profile measuring instrument capable of indicating or recordnigirregularities of the'surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magneticfiux, a tracer point, a'positioning coil, means for connecting said positioning'coil to said tracer point for movement in step with the mechanical displacements thereof, means for mounting said connecting means in saidconverter assembly so as to restrict said tracerpoint to movement substantiallyperpendicular to said specimen surface, said fixed jmagn'etic circuit means having a gap, and said positioning coil being movable in said gap, an'exciting coil for producing alternating magnetic flux in said fixed magnetic circuit means for supplying alternating-current electric power to said exciting coil thus inducing in said positioning coil a voltage whose frequency is that of said alternating-current powerand whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, means for supporting said converter assembly, means for moving said support so that said converter assembly moves substantially parallel to the surface of said specimen under investigation, means for supporting sai'd movable support means,a demodulating circuit including a sensitivity adjusting circuit, an amplifier, an electric wave filter arranged to pass said modulated carrier voltage, and a rectifier arranged to demodulate said amplitude modulated carrier voltage, means for supplying a constant alternating voltage, a second rectifier receiving said alternating voltage and delivering a constant direct-current voltage substantially equal to the direct-current voltage output of said first rectifier, an output network arranged to receive the outputs of said two rectifiers'and subtract said direct-current voltages so as to'leave substantially only said demodulated voltage, an amplifier for amplifying said demodulated voltage, indicating means responsive to said demodulated voltage, said indicating means comprising a graphic recording .means adapted to record on a' suitable medium a graph Whose coordinates aresubstantially proportional to the corresponding dimensions of said irregularities actuating said tracer point.

'11. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point'for movement in step with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantial 1y perpendicular to said specimen surface, fixed electromagnetic means for converting said mechanical displacements. of said positioning coil into amplitude modulations of a constant frequency alternating voltage as said "tracer point is moved along and in contact with the surface of said specimen, a piloting slide for supporting said converterassembly, means for moving said piloting slide so that said converter assembly will move substantially parallel to the surface of said specimen, adjustable means for supporting said piloting slide, a demodulating electric circuit means for receiving said modulated voltage and demodulating same, and means for indicating said demodulated voltage so as to show the irregularities of the surface of said specimen being investigated.

12. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magnetic flux, a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, means for mounting said'connecting'means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular to said specimen surface, said fixed magnetic circuit means having a gap, and said positioning coil being movable in said gap, an exciting coil for producing alternating magnetic fiux in said fixed magnetic circuit means, means for supplying alternating-current electric power to said exciting coil thus inducing in said positioning coil a voltage whole frequency is that of said alternatingcurrent power and whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, a piloting slide for supporting said converter assembly, means for moving said piloting slide so that said converter assembly will move substantially parallel to the surface of said specimen, adjustable means for supporting said piloting slide, a demodulating circuit including a sensitivity adjusting circuit, an amplifier, and a rectifier arranged to demodulate said amplitude modulated carrier voltage, means for supplying a constant alternating voltage, a second rectifier receiving said alternating voltage and delivering a constant direct-current voltage substantially equal to the direct-current voltage output of said first rectifier, an output network arranged to receive the outputs of said two rectifiers and subtract said direct-current voltages so as to leave substantially only said demodulated voltage, indicating means responsive to saiddemodulated voltage, said indicating means comprising a graphic recording means adapted to record on asuitable medium a graph whose coordinates are substan-- tially proportional to the corresponding dimensions of said irregularities actuating said tracer point.

13. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magnetic flux, a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular to said specimen surface, said fixed magnetic circuit means having a gap, and said positioning coil being movable in said gap, an exciting coil for producing alternating magnetic fiux in said fixed magnetic circuit means, means for supplying alternating-current electric power to said exciting coil thus inducing in said positioning coil a voltage whose frequency isthat of said a1- ternating-current power and whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, a piloting slide for supporting said converter assembly, means for moving said piloting slide so that said converter assembly will move substantially parallel to the surface of said specimen, adjustable means for supporting said piloting slide, a demodulating circuit including a sensitivity adjusting circuit, an amplifier, an electric wave filter arranged to pass said modulated carrier voltage, and a rectifier arranged to demodulate said amplitude-modulated carrier voltage, means for supplying a constant alternating voltage, a second rectifier receiving said alternating voltage and delivering a constant direct-current voltage substantially equalto the direct? currentvoltage output of saidfirstrectifier, an: output network arranged to. receivethe outputs ofsaidtwo rectifiers and subtract said direct-cur-a rent voltagesso as to leave substantially only saidv demodulated: voltage, an amplifier for amplifying. said demodulated voltage, and meansfor indicat-. ing said amplified demodulated voltage: so asto show the irregularities of the surface of said specimen being investigated. 7

14. A surface profile measuring instrument. capable of indicating or recording irregularities: of the surfaceof a specimen to be investigated, which comprises a converter assembly including a tracer point, a positioning-coil, means-for. con. nectingsaid positioning coil tosaid tracer point formovement inv stepwith. the mechanical dis.-. placements thereof, means for mountingsaid, connecting means in said converter assembly so as to restrict said-tracer point tomovement subs,

stantiallyperpendicular tov said specimen sur-. face, fixed electromagnetic means forconverting.- said mechanical displacements of said position.-. ing coil into amplitude modulations of a constant frequency alternating voltage as said'tracer point is moved along and in contact With the surface. ofsa-id specimen, a pilotingslide for supporting said converter assembly, means formovin-g said piloting slide so that said converter assembly will move substantially parallel to the surface of said specimen, adjustable means for'supportiug' said piloting slide, a demodulating circuit includ ing a sensitivity adjusting circuit, an amplifier, an electric wave filter arranged'to pass: said mod ulated carrier voltage, and'a rectifier arranged-to demodulate said amplitude-modulated carriervoltage, means for supplying a constant alter. nating voltage, a second rectifierreceiving said alternating voltage and delivering a constant di rect-current voltage substantially equal to thedi-rect-current voltage output of said first rectifier, an output network arranged to receivethe. outputs of said two rectifiers and subtract said direct-current voltages so as to leave substantial lyonly saiddemodulated-voltage, anamplifier for amplifying said demodulated voltage, indicatingv means responsive tosaid demodulated voltage, said indicating means comprising a graphic re cording-means adaptedto-recordon a suitablemedium'a graph whose coordinates are substan tially proportional to the corresponding dim'ensio-nsof said irregularities actuating said tracer 15, A surface profile measuring instrument capable of indicating or recording irregularities. of the surface of a s-p-ecimento be investigated, which comprisesa converter assembly including a fixed magnetic circuit means for carrying alternating magneticflux, a tracerpoint, -a posi-l tioning coil, means for connecting said positioning coil to said tracer point for movement in. step-with the mechanical displacements thereof; means for mounting saidconnecting means in said converter assembly so as to restrict said tracer point to movement substantially.perpen-,.

dicular to said specimen surface, saidfixedmagnetic circuit means having-a gap, and said positioning coil being movable .in-said gap, an excit ingcoil for producing. alternatingqmagnetic flux;

insaidfixed magnetic circuitmeans, meansfor supplying alternating-current electric power to;

said exciting. coil thusinducing in said-positioning coil a voltage whose frequency is that ofsaid alternating-current power and whose amplitude modulated; in, acco danc i hhe ar 1'16: position of said coil with; respect: to. said. fixed; magnetic circuitmea-ns as. said tracer point; moved along and: in contact with: the surface of said. specimen, a; piloting slide-for supporting said;

, converter assembly; means; for moving said pilots,

ing slide so. thatsaid converter assembly: will; move substantially'parallel: to, the surface. of said: specimen, means; for supporting said: piloting. slide; an alinementtable for adj ustablyusu-ppo-r t1: ing said; specimen in. position. for profile investigation, a; demodulating circuitincludinga sensitivity adjusting: circuit-,- an. amplifier,- an electric. wave filter; arranged to. pass said: modulated 0811+ rier voltage, and a. rectifierarranged; to: demodu g late said: amplitude-modulated carrier: voltage;

meanslfor; supplying. a constant alternating: voltage, asecond: rectifier receiving said. alternating. voltage and delivering; a constant direct-.-,cur1:ent-, voltage substantially. equal to the directecurrent.

,voltageoutput of? said first rectifier, an output.

network. arrangedfto. receive the outputs-.ofisaid two rectifier-s. and; subtract said: direct-current. voltages; so as toleave-substantially. only. said def modulated; voltage, an; amplifier for amplifying; said demodulated voltage, indicating meanssre-l sponsive to said demodulated voltage, said:indi1- cat-ing means comprising a graphic recordin means adaptedto record on a; suitable'medium a graph. whosecoordinates. are substantially pro,-v porti-ona-ltto ,thecorresponding dimensions .ofsaidt irregularitieei-a-ctuating, said tracer-point.

1d; A surface profile measuring instrument; capable:. of: indicating; or a recording. irregularities; of the surface of -a,.specimen. to be investi ated; which comprisesavconverter assembly including a tracer point, a positioning; coil, means; fKOT'sCOD-f' nectina said n sitionine ccilz og said.- tracer-..poin o movemen in. step. w th the mech nical: dis: pl cements; hereot. means-- for. mounting saidconnecting I means in said. converter assemblv'sol sto r t ic aid r.acer point o .movementzsubstantially per e dicular tiOi said. sp cimen i.- face;- fixed'ele tromaenet ;me ns .for. convertin saidmechanical. di plac m nts; of; said.=.-nosition.- ingcoil= into; amplitude modulations of: a. con.- stantefrequency-alternating voltage as said tracer; point is: moved along: and in. contact. with; the: surface of said; specimen, a. rotary: supporting means.- for said; converter assembly, meansdor radially adjusting the 'location of said converter assemblyon said. rotary supporting. means, means forrotating said rotary support means, adjustablemeans for mounting andalining saidspecimen in position for profile; investigation; ademcdula-ting electric circuit means-fo-r--:receiving said modulated voltageanddemodulatingsame, and means for indicating said demodulated voltage so as to show'the irregularitiesof thesurface of j saidspecim-en being investigated.-

1 7 surface profile measuring instrumentcape eq d ca ng or recordin rre u ar t es f the surface of a specimen to be investigated, which comprises a converter assembly'including. a fixed magnetic circuit. means for. carrying alter nating' magneticfiux, a tracer point, a posi-. tioning coil, means for connecting. said position-v ing-coilto said tracer point. for movementfin...

step with. the mechanical displacementthereof,

means for -mounting said connecting means in.

neticcircuitmeans having a gap, and said g'DQSitioningcoil beingmovableinsaidgap,anexciting;

coil for producing alternating magnetic-flux'in said-fixed magnetic circuit means, means for supplying alternating-current electric power to said exciting-coil thus inducing -iri 'said positioning coil a voltage whose frequency is that of said alternating current power and whose amplitude is modulated in accordance with the varyingipositionfof said coil with respect 'to's'aid fixed magnetic circuit means as saidtra'cer'point is moved along and in contact with the surface of said specimen, a rotary supporting means for said converter assembly, means for radially adjusting the location of said converter assembly on said rotary supporting means, means for rotating said rotary support means, adjustable means for mounting and alining said specimen in position for profile investigation, a demodulating circuit including a sensitivity adjusting circuit, an amplifier, and a rectifier arranged to demodulate said amplitudemodulated carrier voltage, indicating means responsive to said demodulated voltage, said indicating means comprising a graphic recording means adapted to record on a suitable medium a graph whose coordinates are substantially proportional to the corresponding dimensions of said irregularities actuating said tracer point.

18. A surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated, which comprises a converter assembly including a fixed magnetic circuit means for carrying alternating magnetic flux, a tracer point, a positioning coil, means connecting said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular to said specimen surface, said fixed magnetic circuit means having a gap, and said positioning coil being movable in said gap, an exciting coil for use in producing alternating magnetic flux in said fixed magnetic circuit means, means for supplying alternating-current electric power to said exciting coil thus inducing in said positionin coil a voltage whose frequency is that of said alternating-current power and whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, a rotary supporting means for said converter assembly, means for radially adjusting the location of said converter assembly on said rotary supporting means, adjustable speed means for rotating said rotary support means, adjustable means for mounting and alining said specimen in position for profile investigation, a demodulating circuit including a sensitivity adjusting circuit, an amplifier, and a rectifier arranged to demodulate said amplitude-modulated carrier voltage, means for supplying a constant alternating voltage, a second rectifier receiving said alternating voltage and delivering a constant directcurrent voltage substantially equal to the directcurrent voltage output of said first rectifier, an output network arranged to receive the outputs of said two rectifiers and subtract said directcurrent voltages so as to leave substantially only said demodulated voltage, indicating means responsive to said demodulated voltage, said indicating means comprising a graphic recording means adapted to record on a suitable medium a graph whose coordinates are substantially pro- 18 portional to the corresponding dimensions of said irregularities actuating said 'tracer point.

19. In a surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated and having a movable support adapted to have a converter assembly mounted thereon, :means for moving said support sothat the converter assembly will move substantially parallel to the surface. of said specimen; under investigation, means. for supporting 1 said movable support means, a source of alternating-current carrier power, a demodulating electric circuit means for receiving modulated voltage and demodulating same, and. means for indicating the demodulated voltage so as to show the irregularities of the surface of said specimen being investigated, the combination therewith of a converter assembly mounted on said movable support, said converter assembly including a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular to said specimen surface, means for inductively coupling said source to said positioning coil, fixed electromagnetic means for use in converting said mechanical displacements of said positioning coil into amplitude modulations of said induced voltage in said positioning coil as said tracer point is moved along and in contact with the surface of said specimen, and electric circuit means for operably connecting the amplitude-modulated alternating-current voltage output of said positioning coil to said demodulating electric circuit means.

20. In a surface profile measuring instrument capable of indicating or recording irregularities of the surface of a specimen to be investigated and having a movable support adapted to have a converter assembly mounted thereon, means for moving said support so that the converter assembly will move substantially parallel to the surface of said specimen under investigation, means for supporting said movable support means, a demodulating electric circuit means for receiving modulated voltage and demodulating same, and means for indicating the demodulated voltage so as to show the irregularities of the surface of said specimen being investigated, the combination therewith of a converter assembly mounted on said movable support, said converter assembly including a tracer point, a positioning coil, means for connecting said positioning coil to said tracer point for movement in step with the mechanical displacements thereof, means for mounting said connecting means in said converter assembly so as to restrict said tracer point to movement substantially perpendicular to said specimen surface, a fixed magnetic circuit means having a gap and said positioning coil being movable in said gap, an exciting coil for use in producing alternating magnetic flux in said magnetic circuit means, together with means for supplying alternating-current electric power to said exciting coil thus inducing in said positioning coil a voltage whose frequency is that of said alternating-current power and whose amplitude is modulated in accordance with the varying position of said coil with respect to said fixed magnetic circuit means as said tracer point is moved along and in contact with the surface of said specimen, and electric circuit means for operably connecting the amplitude-modulated constant-frequency voltage Number Name Date 10 w. 7 2,345,022 Williamsan .,..;Mar-. 28,1944 UNITED" STATES PATENTS" 2,411,009.- Reason; Ma:y-24, 1949 2',002',37-2i Greentree 'et:.a1.- May 21,1935 

